Drilling equipment and method

ABSTRACT

A drill bit is provided for drilling holes in hard, reinforced material, including reinforced concrete. According to one aspect of the invention, wear-resistant inserts are provided in a cross-shaped pattern. The inserts ensure that the entire bottom surface of the drilled hole is engaged during each drill bit revolution. The inserts may be secured in pockets or slots. Fluid entry ports may be located between the inserts for efficient handling of drilling fluid and removal of drilled material, without impairing the structural integrity of the drill bit. According to another aspect of the invention, the drilling surface is separated into two or more stages to increase drilling efficiency, especially through composite material such as reinforced concrete.

[0001] This application claims the benefit of U.S. Provisional Application No. 60/192,888, filed Mar. 29, 2000. The entire disclosure of U.S. Provisional Application No. 60/192,888, filed Mar. 29, 2000, is expressly incorporated herein by reference.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates to equipment for drilling and/or excavating hard material, including drill bits and other tools for drilling into and/or through reinforced material. The present invention also relates to a method of drilling a hole in steel reinforced concrete.

[0004] 2. Discussion of the Related Art

[0005] Drill bits for drilling into hard material are known in the art. The known drill bits are unsatisfactory, however. Among other things, the known drill bits are not well suited for drilling large diameter holes in reinforced concrete. Examples of known drill bits and other material handling equipment are shown in U.S. Pat. Nos. 5,326,196 (Noll), 5,161,726 (Francis), 4,056,152 (Lacey), 3,712,753 (Manzi), 2,826,104 (Morin), 2,786,373 (Patton), 2,276,532 (Welty), 1,940,220 (McGrath), 1,747,117 (Klein), 1,387,994 (Lewis), 525,466 (Marsh et al.), and 499,098 (Comstock).

SUMMARY OF THE INVENTION

[0006] The present invention relates to tools, such as drill bits, for forming holes in hard, reinforced material, including reinforced concrete. According to one aspect of the invention, wear-resistant inserts are provided in a cross-shaped pattern. The inserts may be arranged to ensure that the entire bottom surface of the drilled hole is engaged during each revolution of the drill bit. Moreover, fluid entry ports may be located between the inserts for efficient handling of drilling fluid and removal of drilled material. The ports may be located in such a way as to not impair the desired structural integrity of the drill bit. According to another aspect of the invention, the drilling surface (which may be formed by the wear-resistant inserts) is separated into two or more stages to increase drilling efficiency, especially through composite material such as reinforced concrete. In a preferred embodiment of the invention, improved drilling speed through steel reinforcement bars is achieved without significant reduction in the efficiency of drilling through concrete.

[0007] The present invention also relates to a drill tool that has a head portion and inserts for engaging and drilling into hard, reinforced material. The head portion may be provided with conduits and ports for flowing drilling fluid toward the reinforced material, and the inserts may be located in slots in the head portions. The inserts are preferably more wear resistant than the head portion that supports them.

[0008] According to one aspect of the invention, the drill tool may be secured to or integral with a shank that is in turn connected to a drill rig or other drilling apparatus. In operation, the shank applies thrust and torque to the head portion.

[0009] According to another aspect of the invention, fluid passageways are drilled through the head portion to provide fluid communication from an inner portion of the shank to the forward portion of the head portion. The drilled passageways extend along non-parallel paths and intersect each other inside the drill bit. As such, the flow structure for handling the drilling fluid does not degrade the structural integrity of the drill bit. In operation, the drilling fluid may be used to remove drilled material from the cutting edges of the inserts. The drilled material flows along outer paths located along the exterior of the drill bit.

[0010] According to yet another aspect of the invention, the ports for to injecting the drilling fluid into the drilling region are located in recessed portions of the head portion. The recessed portions are such that the ports are spaced axially away from the forward face of the drill bit. The recessed portions are also used to funnel or direct the entrained drilling material into the passageways around the drill bit.

[0011] The inserts may be separated from each other in the plane of their cutting edges. This way, the drilling fluid can flow relatively freely between the inserts to form an efficient flow pattern against the bottom surface of the drilled hole. In a preferred embodiment of the invention, there is an elongated center insert that is surrounded by radial inserts. The radial inserts are arranged to form a cross-shaped pattern. A first group of radial inserts may be longer than the rest of the radial inserts. In one embodiment of the invention, a full face attack cross pattern can be provided, even though none of the inserts extends across the entire forward surface of the head portion. That is, in one embodiment of the invention, the lengths of the cutting edges of the inserts are all much less than the diameter of the head portion. In an alternative embodiment of the invention, one or more of the inserts can extend across the entire forward face of the drill bit.

[0012] According to yet another aspect of the invention, the cutting edges of the wear-resistant inserts each form a roof angle that is in the range of from 34° to about 37°. The desired grade of material, roof-angle, chamfers, size, and orientation of the inserts are preferably constructed so as to obtain maximum cutting speed through steel reinforcement bars with minimal bit wear.

[0013] Further, the present invention also relates to a multi-stage drill bit for forming a cylindrical hole. The drill bit has a pilot stage portion and at least one subsequent stage. The pilot stage may be provided with the ports mentioned above for flowing drilling fluid into the pilot hole, and wear-resistant inserts for engaging the drilled material. The second or subsequent stage has a larger diameter than the pilot stage to increase the size of the drilled hole. In a referred embodiment of the invention, the second stage is also provided with wear-resistant inserts.

[0014] In addition, the present invention relates to a method of drilling a hole into reinforced concrete. The method includes the steps of (1) using a pilot stage to drill through a steel reinforcement bar; (2) using a larger diameter second stage to drill through the reinforcement bar; and (3) transmitting torque from the shank to the pilot stage through the larger diameter second stage.

[0015] These and other features of the invention will become apparent from the following detailed description of preferred embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

[0016]FIG. 1 is an end view of a drill bit constructed in accordance with one embodiment of the present invention.

[0017]FIG. 2 is a partial cross-sectional view of the drill bit of FIG. 1, taken along the line 2-2.

[0018]FIG. 3 is a partial cross-sectional view of the drill bit of FIG. 1, taken along the line 3-3.

[0019]FIG. 4 is a perspective view of a drill bit constructed in accordance with another embodiment of the present invention.

[0020]FIG. 5 is an end view of the drill bit of FIG. 4.

[0021]FIG. 6 is a cross-sectional view of the drill bit of FIG. 4, taken along the line 6-6 of FIG. 7.

[0022]FIG. 7 is a partial cross-sectional view of the drill bit of FIG. 4, taken along the line 7-7 of FIG. 5.

[0023]FIG. 8 is partial cross-sectional view of the drill bit of FIG. 4, taken along the line 8-8 of FIG. 5.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0024] Referring now to the drawings, where like reference numerals designate like elements, there is shown in FIG. 1 a drill bit 10 constructed in accordance with the present invention. The drill bit 10 is well suited for drilling through reinforced concrete and/or other composite materials. The drill bit 10 has a shank 12 (FIG. 2), a larger diameter head portion 14, long radial inserts 16, 18, short radial inserts 20, 22 (FIG. 1), and a center insert 24. The shank 10 and the head portion 14 may be made of steel or another suitable material. The inserts 16-24 may be formed of tungsten carbide, or another suitable wear-resistant material. In a preferred embodiment of the invention, the inserts 16-24 are designed to drill through steel reinforcing rods and/or other tough materials embedded in concrete.

[0025] The inserts 16-24 are located within respective slots or pockets 26, 28, 30, 32, 34. The inserts 16-24 are sized to fit snugly within the slots 26-34. If desired, the inserts 16-24 may be connected to the forward face 36 of the head portion 14 by a suitable brazing material (not shown). The inserts 16-24 have grinding or cutting edges 38, 40, 42, 44, 46 that lie within a common plane. In the illustrated embodiment, the cutting plane (contains the edges 38-46) is perpendicular to the rotational axis of the drill bit 10. Each cutting edge 38-46 forms a roof angle α (FIG. 2) that is in the range of from about 34° to 37°.

[0026] In operation, an axial force is applied by the shank 12 in the direction of arrow 60 to press the cutting edges 38-46 against the bottom of the hole being drilled (not shown), and a torque is simultaneously transmitted through the shank 12 in the direction of arrow 62 (FIG. 1) to rotate the cutting edges 38-46 to grind or drill the bottom surface of the hole. Drilling fluid (not shown) flows through the center of the shank 12 in the direction of arrow 60, and then through four conduits (only two of which are shown in FIG. 3 designated by reference numerals 67, 69) and ports 66, 68, 70, 72 (FIG. 1) toward the bottom surface of the hole.

[0027] Each of the four ports 66-72 is connected to a respective one of the four conduits 67, 69. There may be four conduits 67, 69—one for each port 66-72, although only two conduits are shown in FIG. 3 for the sake of clarity. The other two conduits would be seen on another cross section through the drill bit 10, extending from the respective ports to the center of the shank 12. In the preferred embodiment of the invention, there are four conduits 67, 69 and four respective ports 66-72. The present invention should not be limited, however, to the specifics of the preferred embodiments shown and described in detail herein.

[0028] The drilling fluid may be liquid or air, for example. The drilling fluid entrains drilled material from the bottom of the hole and transmits it through scalloped passageways 74, 76, 78, 80 formed in the cylindrical side surface 82 of the head portion 14. The drilled material flows with the drilling fluid away from the bottom of the hole in the direction of arrow 84 (FIG. 2).

[0029] If desired, the shank 12 may be connected to a drill rig or extension (not shown) by an internal rope thread 86 (FIG. 3) or by another suitable connection mechanism. Other connection threads can be provided with adapters or during manufacture of the bits. In an alternative embodiment of the invention, the bit 10 is permanently mounted on a drill string (not shown) of any suitable length.

[0030] As shown in FIG. 1, the length of the cutting edge 46 of the center insert 24, along with the lengths and locations of the radial inserts 16-22 provide radial overlap. This way, the entire circular surface of the hole is excavated as the bit 10 is rotated. In other words, as the bit 10 is rotated in the hole, the sweep of the cutter inserts 16-24 engages and cuts every part of the hole face. Preferably, the entire circular surface of the drilled hole facing the cutting edges 38-46 is engaged by the cutting edges 38-46 during each rotation of the drill bit 10. In the illustrated embodiment of the invention, the center cutting edge 46 is longer than the long radial edges 38, 40, and the long radial cutting edges 38, 40 are longer than the short radial cutting edges 42, 44. The present invention should not be limited, however, to the preferred embodiments shown and described in detail herein.

[0031] If desired, concave or recessed portions 90, 92, 94, 96 may be provided for spacing the conduit openings or ports 66-72 axially away from the forward face 36 of the head portion 14. In the illustrated embodiment, there is one concave portion 90-96 for each port 66-72. If desired, however, the invention may be practiced with more or less than four concave portions 90-96 and ports 66-72. Preferably, the concave portions 90-96 form funnel-like structures that help to guide or direct the drilling fluid into the respective scalloped passageways 74-80. The conduits 67, 69 connecting the ports 66-72 to the shank 12 are formed by drills to have constant diameters. The conduits 67, 69 extend in straight lines from the recessed portions 90-96 to a common point 71 where they meet at the central axis of the shank 12. This way, the conduits 67, 69 do not degrade the structural integrity of the drill bit 10.

[0032] The drill bit 10 may have an operating diameter 98 (FIG. 2) that is in the range of from about one inch to about two and one-half inches. Thus, for example, the drill bit 10 may be used to drill a hole into 5000 psi compressive strength concrete made of crushed limestone aggregate, reinforced with number 11 rebar (steel reinforcement bars) on four-inch centers each face, each way. The drill apparatus may have an operating pressure of about 2250 pounds per square inch; the impact energy may be between about 100 to 120 foot-pounds; the impact frequency may be between about 3300 to 3600 bpm; with a rotation speed of about 0 to 250 rpm. In operation, the bit 10 of the present invention, with an outside diameter in the range of from about 1.25 to 2.00 inches may provide a drilling speed that is 20% to 40% higher than can be achieved by conventional cross-face bits. The present invention should not be limited, however, to the preferred embodiments shown and described herein.

[0033] Referring now to FIG. 4, there is shown a two-stage drill bit 100 constructed in accordance with another aspect of the present invention. The two-stage bit 100 provides multiple attack stages to reduce the total area of rebar being excavated at any one time. The first stage (or pilot stage) 102 has the inserts 16-24, ports 66-72, recessed areas 90-96, and downstream fluid pathways 74-80 of the drill bit 10 of FIGS. 1-3. The first stage 102 is followed by a larger diameter second stage 104. The second stage 104 has four inserts 106, 108, 110, 112 (FIG. 5) with cutting edges 114, 116, 118, 120 (FIG. 6) that are constructed like the cutting edges 38-46 of the first stage 102. The second stage inserts 106-112 are separated from each other by recessed portions 122, 124, 126, 128 that funnel the drilling fluid into scalloped passageways 130, 132, 134, 136.

[0034] In operation, the drilling fluid that flows axially out the drilled hole, through the scalloped passageways 74-80 of the first stage 102, in the manner explained above in connection with FIGS. 1-3, subsequently flows into the recessed portions 122-128 of the second stage 104. The drilling fluid picks up additional drilled material from the second stage 104 and is funneled into the second stage outbound passageways 130-136. Thus, the drilling fluid (with the entrained drilled material) flows axially out of the drilled hole around the second stage 104 in the direction of arrow 138.

[0035] In the illustrated embodiment, the first stage 102 is integral with the second stage 104, and the second stage 104 is integral with a shank 12. Thus, the axial force (60) and torque (62) applied by the shank 12 are applied through the second stage 104 to the second and pilot stage inserts 16-24, 106-112.

[0036] In operation, the two stages 102, 104 work together to expand the hole in the concrete to the desired larger diameter. When rebar (not shown) is encountered, the total “crowd force” available from the drill rig is distributed by the drill bit 100 largely on the rebar until it is excavated by the smaller-diameter pilot stage 102. That is, the pilot stage 102, 16-24 drills through a length of the rebar equal to approximately the width 98 of the pilot stage 102. The second and first stages 102, 104 then excavate through concrete together until the second stage 104 encounters the rebar. At this point, the total “crowd force” of the drill rig is largely acting on the excavation of the rebar through contact with the cutting edges 114-120 of the second stage 104. Eventually, lengths of the rebar approximately equal to the lengths of the second stage cutting edges 114-120 are drilled on either side of the portion of the rebar that was drilled through by the pilot stage 102. The decrease in bit area (compared to the entire cross sectional area of the fully drilled hole) acting on the rebar at any one time increases the overall drilling efficiency. The pilot stage performance of the bit 100 also assists in drilling a straight hole.

[0037] The two-stage drill bit has four ports 66-72 and four respective conduits 101, 103 (only two of the conduits are shown in FIG. 8 for the sake of clarity of illustration). That is, the four ports 66-72 are connected to the annular interior of the bit 100 by four respective drilled passageways 101, 103. The ports 66-72 provide ample flow of drilling fluid to the drilling surface (i.e., the bottom of the drilled hole) without degrading the structural integrity of the bit 100. The ports 66-72 may be present only on the pilot stage 102, since the fluid will flow from the pilot stage 102 and wash over the second stage 104. If additional flow is necessary on the second stage 104 for especially difficult applications, additional ports (not shown) and drilled flow passageways (not shown) may be added to the second stage 104, if desired.

[0038] The two-stage bit 100 provides the full-face attack construction of the bit 10 of FIGS. 1-3. In addition, the two-stage bit 100 provides improved drilling speed through reinforced concrete especially where the diameter of the hole being drilled is greater than about two-inches (or greater than the thickness of the rebar).

[0039] While preferred embodiments of the invention have been described and illustrated, it should be apparent that many modifications can be made to the preferred embodiments without departing from the spirit or scope of the present invention. Accordingly, the invention is not limited by the foregoing description or drawings, but is only limited by the scope of the appended claims. 

What is claimed as new and desired to be protected by Letters Patent of the United States is:
 1. A drill tool for drilling into reinforced material, said drill bit comprising: a head portion having ports for flowing drilling fluid toward said reinforced material, said head portion being formed of a first material; and inserts for engaging said reinforced material, said inserts being located in said head portion, said inserts being formed of a second material, and said second material having greater wear resistance than said first material.
 2. The drill tool of claim 1, further comprising a shank for applying axial thrust and torque to said head portion.
 3. The drill tool of claim 2, further comprising drilled passageways for providing fluid communication from an inner portion of said shank to said ports of said head portion.
 4. The drill tool of claim 3, wherein said drilled passageways intersect each other in said inner portion of said shank.
 5. The drill tool of claim 1, further comprising outer passageways formed in an outer surface of said head portion for flowing said drilling fluid away from said inserts.
 6. The drill tool of claim 5, further comprising recessed portions in said head portion for directing said drilling fluid toward said outer passageways.
 7. The drill tool of claim 6, wherein said ports are located in said recessed portions.
 8. The drill tool of claim 1, wherein said inserts include a center insert surrounded by first and second radial inserts forming a cross-shaped pattern.
 9. The drill tool of claim 8, wherein the length of said center insert is greater than the width of said first and second radial inserts.
 10. The drill tool of claim 9, wherein said second radial inserts are longer than said first radial inserts.
 11. A multi-stage drill bit for forming a cylindrical hole in a reinforced material, said multi-stage drill bit comprising: a pilot stage for forming a pilot hole, said pilot stage including ports for flowing drilling fluid into said pilot hole, and wear-resistant inserts for engaging said reinforced material; and a second stage for enlarging said pilot hole, said second stage having a greater diameter than said pilot stage, and said second stage including inserts.
 12. The multi-stage drill bit of claim 11, wherein said wear-resistant inserts of said pilot stage and said second stage have cutting edges with a roof angle in the range of from about 34 to 37 degrees.
 13. The multi-stage drill bit of claim 12, wherein said cutting edges are formed of wear-resistant material.
 14. The multi-stage drill bit of claim 13, wherein said pilot stage and said second stage include passageways for directing drilling fluid away from said inserts.
 15. A method of drilling a hole into reinforced concrete, said method comprising the steps of: using a pilot stage to drill through a metal reinforcement bar; and subsequently, using a larger diameter second stage to drill through said reinforcement bar; and transmitting torque through said larger diameter second stage to said pilot stage.
 16. The method of claim 15, further comprising the step of flowing drilling fluid through interior passageways in said pilot stage.
 17. The method of claim 16, further comprising the step of flowing said drilling fluid and drilled material around said second stage.
 18. The method of claim 16, wherein said step of using said pilot stage to drill though said reinforcement bar includes the step of engaging said bar with wear-resistant inserts.
 19. The method of claim 18, wherein an elongated central insert forms a central portion of said pilot hole, and radially outer inserts form an annular portion of said pilot hole surrounding said central portion of said pilot hole, such that said inserts define overlapping rotational paths that together cover the entire attack face of said pilot stage.
 20. The method of claim 19, wherein fluid flow ports are located between said radially outer inserts. 